This invention relates to air compressors; and more particularly relates to novel and improved forms of guide assemblies for guiding the reciprocal movement of a swash plate.
In the past, air compressors have borrowed from conventional combustion engine designs while reversing the typical energy cycle to convert mechanical energy into pneumatic energy. Indeed, most prior air compressors utilize conventional crankshaft technology to drive pistons and thus suffer numerous drawbacks relating to energy conversion, size and weight, as well as the noise associated with operation of such compressors.
With the advent of smaller motors, the size and weight of compressors have gradually been reduced, allowing portable compressors to be attached to relatively small air tanks. However, such portable compressors still typically rely on traditional crank shaft technology and thus trade power for size so that most portable compressors can not achieve substantial volume at high pressure within the attached air tank. Furthermore, even with their reduced size, such portable air compressors and their associated air tanks represent heavy, cumbersome assemblies which strain the definition of the term xe2x80x9cportable.xe2x80x9d
A further drawback to current compressors is that the compressor is typically mated with a single air tank and can not be easily adapted to work with other air tanks. Thus, current portable compressors are often relegated to being used with small air tanks which may be too small to hold a useful volume of pressurized air for the required task. Similarly, larger non-portable air tanks are typically mated with large compressors which can not be easily moved.
Previously, efforts have been made to substitute swash plate technology for the more conventional crank shaft technology within air compressors. Swash plate compressors utilize a wobbling disk connected to a drive shaft to reciprocate the pistons within the air cylinders. Due to the relatively small size of most air compressors (at least in relation to the size of an internal combustion engine), the use of a wobble or swash plate to drive the pistons has led to increased efficiencies due to the decreased angle of the piston connecting rod which is attached to the swash plate and the mechanical flow of energy. In essence, the swash plate provides a truer reciprocating action for the piston rods than is possible with conventional crank shafts. This has led to the introduction of oil or lubricant-free compressors due to the reduced strain applied by the swash plate to the piston connecting rods which results in reduced friction between the pistons and cylinders.
However, these early swash plate compressors have failed to adequately address the added degree of motion which the swash plate imposes on the piston connecting rod in comparison to a traditional crank shaft. In essence, the wobbling motion of the swash plate causes a periphery of the swash plate to follow a wave-like or FIG. 8 pattern which results from the combination of a first arcuate motion of the swash plate periphery toward and away from the drive shaft and a second rolling motion of the swash plate periphery about an axis perpendicular to the drive shaft. To account for this FIG. 8 pattern, the end of the piston connecting rod which is connected to the swash plate must be free to move in two different directions (i.e., rotate about two different axes) to prevent over-stressing the piston rods. While some designs have attempted to provide for this freedom of movement by replacing traditional piston connecting rod, bearings and wrist pins with ball and socket connectors or other similar joints, these joints have failed to provide an adequate connection between the swash plate and the piston rod, particularly when the compressor is required to achieve high pressures or is operated over extended duty cycles. Specifically, prior swash plate compressors utilizing ball and socket connectors are typically not suitable to generate relatively high pressures (e.g., 90 p.s.i. and above) and are extremely susceptible to piston rod failure.
Representative of such prior swash plate compressors are those disclosed in U.S. Pat. No. 2,825,499 to Gibson et al., U.S. Pat. No. 4,495,855 to Murakami et al., U.S. Pat. No. 5,109,754 to Shaw, and U.S. Pat. No. 5,304,043 to Shilling, each of which use ball and socket connectors or similar swivel elements within the swash plate to engage the piston connecting rods. Other patents of interest include U.S. Pat. No. 4,734,013 to Valavaara, U.S. Pat. No. 5,127,314 to Swain, U.S. Pat. No. 2,956,845 to Wahlmark, and U.S. Pat. No. 2,412,316 to Campbell.
There is a continuing need for novel and improved swash plate compressors which are capable of minimizing power consumption, vibration and noise while being further characterized by their simplified construction.
It is therefore an object of the present invention to provide for novel and improved forms of swash plate air compressors which are compact and highly efficient in operation.
Another object of the present invention is to provide for novel and improved guide means for stabilizing precessional movement of a swash plate with minimal power loss and maximum efficiency.
In a preferred form of swash plate compressor, a swash plate is connected to a drive shaft from a motor by an angled cam hub and bearing to translate rotational motion of the shaft into reciprocal motion of the swash plate with a plurality of pneumatic cylinders each including a piston driven by a piston connecting rod connected to the swash plate, and means for connecting a first end of the piston connecting rod to the periphery of the swash plate which includes means for rotating the first end of the piston connecting rod about a first axis substantially perpendicular to the drive axis and means for rotating the first end of the piston connecting rod about a second axis substantially perpendicular both to the first axis and drive axis. The connecting means is further characterized by a plurality of U-shaped slots on the periphery of the swash plate for connecting the first ends of the piston rods wherein the means for rotating the first end of each piston rod about a first axis includes a pair of annular bearings positioned within a pair of openings in opposite sides of each slot and an axle having opposed ends seated within bearings in opposite sides of the slot to allow the axle to rotate about the first axis.
In the modified forms of the invention, one employs a linear guide bracket to cooperate in guiding the vertical movement of the swash plate in driving the pistons with respect to the cylinders of the air compressor. In another form, the swash plate is stabilized in its movement by an upper static plate with directional rollers cooperating with mating grooves in stabilizing movement of the swash plate as it drives the pistons. Both of the modified forms to be hereinafter described in more detail are preferably used in cooperation with a centrifugal force governor which is installed on the drive shaft to release the air pressure in the manifold and achieve enhanced compressor performance.
The above and other objects, advantages and features of the present invention will become more readily appreciated and understood from a consideration of the following detailed description of preferred and modified forms of the present invention when taken together with the accompanying drawings in which: